Shell Architecture Strongly Influences the Glass Transition, Surface Mobility, and Elasticity of Polymer Core-Shell Nanoparticles

Abstract

Despite the growing application of nanostructured polymeric materials, there still remains a large gap in our understanding of polymer mechanics and thermal stability under confinement and near polymer–polymer interfaces. In particular, the knowledge of polymer nanoparticle thermal stability and mechanics is of great importance for their application in drug delivery, phononics, and photonics. Here, we quantified the effects of a polymer shell layer on the modulus and glass-transition temperature ( T g ) of polymer core–shell nanoparticles via Brillouin light spectroscopy and modulated differential scanning calorimetry, respectively. Nanoparticles consisting of a polystyrene (PS) core and shell layers of poly( n -butyl methacrylate) (PBMA) were characterized as model systems. We found that the high T g of the PS core was largely unaffected by the presence of an outer polymer shell, whereas the lower T g of the PBMA shell layer decreased with increasing PBMA thickness. The surface mobility was revealed at a temperature about 15 K lower than the T g of the PBMA shell layer. Overall, the modulus of the core–shell nanoparticles decreased with increasing PBMA shell layer thickness. These results suggest that the nanoparticle modulus and T g can be tuned independently through the control of nanoparticle composition and architecture.

Direct Visualization and Characterization of Interfacially Adsorbed Polymer atop Nanoparticles and within Nanocomposites

“…We further confirmed the formation and stability of irreversibly absorbed layers atop the NPs via BLS, a labelfree, contactless, nondestructive technique which probes highfrequency NP elastic vibrations. 49 In accordance with previous studies of soft core−thin shell polymer NPs, BLS measurements of colloidal clusters of PS/SiO x shell−core NPs indicated that the quadrupolar (1, 2) mode 58,59 denoting shearing motion on the NP surfacewas sensitive to NP surface dynamics. Figure 3a shows the evolution of the BLS I(f) spectrum as a function of t ann .…”

Local Glass Transition Temperature Tg(z) Within Polystyrene Is Strongly Impacted by the Modulus of the Neighboring PDMS Domain

“…Glassy–rubbery interfaces between polymer domains impart material toughness and flexibility , and can be used to tune phononic transport . Although a range of different processing methods have been developed to create morphologies with sub-100 nm domain sizes, − studies of simplified systems with a single interface can directly inform the underlying mechanisms behind such applications by mapping local properties as a function of distance from the interface.…”

Reaching the Ideal Glass in Polymer Spheres: Thermodynamics and Vibrational Density of States

“…Spheres with diameter 150 nm fulfil this criterion as extensively discussed in the Supplemental Material [40], which includes Refs. [45][46][47][48][49][50][51][52][53][54][55][56][57][58]. Characterizing the time evolution of the enthalpy, that is, the energy at constant pressure, in terms of T f during physical aging by means of differential scanning calorimetry (DSC), we find that accessing low energy states well below T g is triggered by a fast mechanism of equilibrium recovery, widely characterized in recent years [12,59,60].…”